fix(array): add nil checks in Data.Release() for childData (#456)

### Rationale for this change

My program crashed with below log

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x53beb92]

goroutine 294 [running]:
github.com/apache/arrow-go/v18/arrow/array.(*Data).Release(0xc02586a5b0)
        /root/go/pkg/mod/github.com/apache/arrow-go/v18@v18.4.0/arrow/array/data.go:150 +0x172
github.com/apache/arrow-go/v18/arrow/array.concat.func1()
        /root/go/pkg/mod/github.com/apache/arrow-go/v18@v18.4.0/arrow/array/concat.go:528 +0x9c
github.com/apache/arrow-go/v18/arrow/array.concat({0xc14ae66008, 0x100, 0x100}, {0x83213c0, 0xb026080})
        /root/go/pkg/mod/github.com/apache/arrow-go/v18@v18.4.0/arrow/array/concat.go:652 +0x3f7d
github.com/apache/arrow-go/v18/arrow/array.Concatenate({0xc104861908, 0x100, 0x12f}, {0x83213c0, 0xb026080})
        /root/go/pkg/mod/github.com/apache/arrow-go/v18@v18.4.0/arrow/array/concat.go:55 +0x585
...
```

### What changes are included in this PR?

Add nil check in Data.Release() for childData to avoid crash.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.

Author: secfree

arrow/array/data.go

@@ -147,7 +147,9 @@ func (d *Data) Release() {
 		}
 
 		for _, b := range d.childData {
-			b.Release()
+			if b != nil {
+				b.Release()
+			}
 		}
 
 		if d.dictionary != nil {

arrow/array/data_test.go

@@ -136,3 +136,22 @@ func TestSizeInBytes(t *testing.T) {
 		}
 	})
 }
+
+func TestDataReleaseWithNilChildData(t *testing.T) {
+	mem := memory.NewCheckedAllocator(memory.DefaultAllocator)
+	defer mem.AssertSize(t, 0)
+
+	// Create a Data object that simulates the state after a failed concatenation
+	// where childData slice is allocated but contains nil elements
+	buffers := []*memory.Buffer{memory.NewBufferBytes([]byte("test-buffer"))}
+	data := NewData(arrow.ListOf(arrow.PrimitiveTypes.Int32), 1, buffers, nil, 0, 0)
+
+	// Simulate the scenario where childData is allocated but elements remain nil
+	// This happens in concat.go when childData is allocated but concat() fails
+	data.childData = make([]arrow.ArrayData, 1)
+	// data.childData[0] remains nil (simulating failed concat)
+
+	assert.NotPanics(t, func() {
+		data.Release()
+	}, "Release() should not panic when childData contains nil elements")
+}